Can I temporarily swap out the coil in my '74 CS(i) with one from a '89 Saab Turbo (Bosch, of course) to rule out a coil problem (trying to eliminate possible causes of seriously poor running..it could be a D-jet problem.) The coil in my coupe doesn't have a ballast resistor ('74s use a resistance wire in place of the resistor, one of many things that make '74s so unique) and I don't know if it's "internally ballasted" or not. I figure a short-term test wouldn't hurt, or am I nuts?
Ignition coil...seen one, seen them all?
- Thread starter bill
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The stock coil with a resistor wire is 3 ohms, same as a stock coil and ballast resistor. As long as you have 3 ohms I would think you are fine but for trouble shooting I would give it a try.
tochi
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Not so sure you can judge a coil by it's looks. I could be wrong but your '89 SAAB probably uses a transistorized ignition module, versus the kettering ignition points-triggered system used in the majority of E9s. (Of course, some E9s employed transistorized ignitions, but it "seems" that they were in the minority.) Sight unseen, I would guess that the SAAB coil's resistance is lower than the 3 ohms HBChris mentioned. I don't pretend to know the original equipment specs for a 74 csi, but 3 ohms seems more in line with the replacement blue coil (often , but not always, internally resisted) rather than the originally installed black coil, which did require an external ballast resistor.
Curiously, the undated so-called late model owner's manual found elsewhere on this site indicates "9" ohms, although it probably should read "0.9" or ~1ohm.
Although it probably offered no significant advantage, what used to be labeled the red coil (with more windings), generally required a 1.8 ohm ballast resistor. ("Generally," because for every rule there seems to be an exception.) https://e9coupe.com/forum/threads/ignition-coil.22231/
So, in answer to your question, the short-term test contemplated would "probably" not cause any problems.
Just thought with 12 volt coils both made by Bosch there wouldn't be much difference except for internal ballast. If the resistances measure close, then for a short-term test I wouldn't think it would matter much.
Thanks Tochi.
Thanks Tochi.
bosch coils are different in later BMWs, my e12 has an electronic ignition with a unique coil, and another is used for the b35, even the center post is different.